This Spring Derek Parfit is Visiting Professor of Philosophy at Harvard University, where he is teaching "Recent Ethical Theory" with TM. Scanlon. Professor Parfit is a Fellow of All Souls College, Oxford. He is the author of Reasons and Persons, and has written extensively on ethics and personal identity.

There two questions: → (1) Why does the Universe exist at all? That is, why is there anything rather than nothing? → (2) Why is the Universe as it is?

Some dismiss these questions, thinking them idle. Some even think they make no sense. I believe they are both good questions, which could at least have partial answers.

The Universe could have been, in countless ways, different. Even if its features were in no way special, it would be puzzling why, out of all possible Universes, this is the one that exists. This fact would seem arbitrary. Moreover, the Universe does seem to be special. For example, physicists now believe that if things had been very slightly different, in a whole range of ways, life would have been impossible. Can this be merely a coincidence? Theists answer No. On their view, God created the Universe with these special features. It would not be surprising that God should have wanted life to be possible. But we could still ask why, among the possible life-containing Universes, God chose this one to be actual. If this was the best possible Universe, or was at least very good, this question would be answered. But, to defend this answer, we would have to solve the problem of evil.

If we could solve that problem, and could assume that God exists, question (2) would be answered. And question (1) might be less puzzling. This question would become, 'Why does God exist?' We partially explain some phenomenon if we show it be simpler, and less arbitrary. Compared with the existence of a highly complicated and specific Universe, God's existence may be claimed to have these features.

There is a different view. Suppose that the observable Universe were only a fraction of reality. Suppose, most simply, that all possible Universes were actual. (See "Nozick (Robert) - Philosophical Explanations", Chapter Two – "Nozick (Robert) - Why Is There Something Rather Than Nothing?".) Question (2) would then disappear. If ours is the only actual universe, it makes sense to ask, 'Why is the Universe the way it is?' since we are then asking, 'Out of all the possibilities, why is this the one that is actual?' But, if all possibilities were actual, there would be no such question. Nor could we sensibly ask, 'Why is our Universe the one it is?' That would be like asking 'Why are we who we are?', or 'Why is it now the time that it is?' And it would not be surprising that our universe was one of those where life is possible.

Besides dissolving question (2), this 'many worlds' hypothesis would also make question (1) less puzzling. If all possibilities were actual this would need less explanation than if only one was actual. But we could still ask, 'Why is anything actual? Why is there anything rather than nothing?'

If these hypotheses would give partial answers to our questions, is this a reason to believe them? If so, how should we choose between them? And could we go beyond them? Is there an answer that leaves nothing unexplained?

We could not causally explain either why God exists, or why there is anything rather than nothing. There might perhaps be a causal law, as some physicists suggest, which allowed something to arise from nothing. But there could not be a causal explanation of why this law held. Could there be an explanation of some other kind?

On one view, God necessarily exists. This could be claimed, instead, of the Universe. If such a view made sense, and was true, there would be nothing that was unexplained. If something necessarily exists, there is no conceivable alternative. But there are well-known objections to this kind of view.

According to another view, God exists because he ought to: because it is good that he exists. As before, this could be claimed directly of the Universe. Since this view does not claim that either God or the Universe necessarily exists, it may escape the objections to that claim. If this view were true, there would still be something that was unexplained. We could still ask why this view was true: why things exist because they ought to. But there would be less to be explained. As an answer to the question, 'Why do things exist?', 'Because they ought to' would be better than 'For no reason.'

Such a view once again raises the problem of evil. The Universe appears to be flawed. If things exist because they ought to, why are they not much better than they are?

A partial answer might come from a variant of the many worlds hypothesis. Perhaps, in the wider scheme of things, every good Universe exists. It would then not be puzzling why things are not much better than they are. If all good possibilities are actual, things are on the whole, much better. They are better elsewhere. It might then be enough if there were no injustice in the way things are here.

We may instead take a bleaker view. There may be no connection between goodness and reality. Things may exist, not because they ought to, but for some other reason. Or there may be no such reason. The Universe may be inexplicable.

What are the implications of these views? Would God's existence, or non-existence, make a difference to morality? How should we react to the many worlds hypothesis? If the Universe was morally neutral, or inexplicable, how should this affect our attitudes to our own lives? What would we then have reason to care about, or do? φ